Synchronization signal sending method and receiving method, and apparatus

ABSTRACT

Example synchronization signal sending and receiving methods and apparatus are described. In one example method, a terminal device determines a target frequency resource. A frequency domain position of the target frequency resource is determined based on a frequency domain position offset and a frequency interval of synchronization channels. The terminal device receives a synchronization signal by using the target frequency resource.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/860,963, filed on Apr. 28, 2020, which is a continuation of U.S.patent application Ser. No. 16/355,024, filed on Mar. 15, 2019, now U.S.Pat. No. 10,652,070, which is a continuation of InternationalApplication No. PCT/CN2017/103862, filed on Sep. 28, 2017, which claimspriority to Chinese Patent Application No. 201610884855.4, filed on Oct.10, 2016. All of the afore-mentioned patent applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This application relates to the communication field, and in particular,to a synchronization signal sending method and receiving method, and anapparatus.

BACKGROUND

Currently, in a Long Term Evolution (LTE) system, a synchronizationchannel used for cell synchronization and cell search is located at acenter of a system bandwidth. Using a system whose bandwidth is 20 MHzas an example, a frequency domain position of the synchronizationchannel is shown in FIG. 1 . In the LTE system, before accessing thesystem, UE needs to search for a synchronization signal (SS). After asynchronization signal is found, the UE can determine a frequency domainposition of a center frequency of the system and timing synchronizationinformation and frequency synchronization information. To reducecomplexity of searching for a synchronization signal by the UE, an LTEprotocol defines that a synchronization channel needs to be located at afrequency that is an integer multiple of 100 kHz in frequency domain,for example, 2 MHz, 2.1 MHz, or 2.2 MHz. Equal intervals of 100 kHz arechannel rasters of the synchronization channel in the LTE protocol.

In the future Fifth Generation (5G) mobile communication system, thesystem may need to send synchronization signals in a same time resourcein a frequency division manner because of requirements such as multipleservice co-existence or multi-beam sending, and all the synchronizationsignals need to be mapped to a candidate frequency domain position setof a synchronization channel. If the candidate frequency domain positionset of the synchronization channel still uses the design of 100 kHzchannel rasters in LTE, 100 kHz does not match a size of a frequencydomain resource occupied by a physical resource block (PRB) in the 5Gsystem, and therefore, it needs to ensure that all the synchronizationsignals align with boundaries of PRBs during mapping of synchronizationsignals, so as to minimize physical resource block overheads of thesynchronization signals in the system. In this case, available mappingpositions for synchronization signals are greatly limited, and an actualvalue of the channel raster of the synchronization channel is a leastcommon multiple of a frequency bandwidth of the PRB and 100 kHz. In anexample that the PRB occupies 180 kHz, an actual value of the channelraster of the synchronization channel is 900 kHz, and thesynchronization signals need to be mapped to a position determined basedon the channel raster of 900 kHz. This greatly limits availablefrequency domain mapping positions for the synchronization signal.

SUMMARY

Embodiments of this application provide a synchronization signal sendingmethod and receiving method, and an apparatus, so as to increaseavailable frequency domain mapping positions for a synchronizationsignal.

According to a first aspect, a synchronization signal sending method isprovided, including:

determining a target frequency resource, where a frequency domainposition of the target frequency resource is determined based on afrequency interval of synchronization channels, the frequency intervalof synchronization channels is 2^(m) times a predefined frequencybandwidth of a frequency resource of a physical resource block, and m isa preset nonnegative integer; and

sending a synchronization signal by using the target frequency resource.

The frequency domain position of the frequency resource occupied by thesynchronization signal is determined based on the frequency interval ofsynchronization channels, and the frequency interval of synchronizationchannels is 2^(m) times the predefined frequency bandwidth of thefrequency resource of a physical resource block. This is for the benefitof increasing a quantity of candidate frequency resources ofsynchronization signals, thereby increasing available frequency domainmapping positions for the synchronization signal.

In a possible implementation, a starting frequency domain position or anending frequency domain position of the target frequency resource alignswith a boundary of a physical resource block of a data channel.

This can prevent the synchronization signal from occupying an extraphysical resource block, and reduce physical resource block overheads ofthe synchronization signal in a system, thereby improving physicalresource block utilization of the system.

In a possible implementation, the frequency domain position of thetarget frequency resource is determined based on the frequency intervalof synchronization channels and a preset frequency domain positionoffset.

The available frequency domain mapping positions for the synchronizationsignal can be further increased by flexibly defining a value of thefrequency domain position offset.

In a possible implementation, the frequency domain position of thetarget frequency resource is determined according to the followingrelational expression:

p=offset+n*frequency_interval,

where p is the frequency domain position of the target frequencyresource, offset is the frequency domain position offset, n is a presetinteger, and frequency_interval is the frequency interval ofsynchronization channels.

In a possible implementation, n is an integer in an integer set that isdetermined based on a frequency band used by a system.

In this way, candidate frequency resources of the synchronization signalcan be set flexibly based on the frequency band used by the system,thereby further increasing the available frequency domain mappingpositions for the synchronization signal.

In a possible implementation, there is a correspondence between thefrequency band used by the system and the frequency domain positionoffset and/or the frequency interval of synchronization channels, and avalue range of m is determined based on the frequency band used by thesystem.

In this way, candidate frequency resources of the synchronization signalcan be set flexibly based on the frequency band used by the system,thereby further increasing the available frequency domain mappingpositions for the synchronization signal.

In a possible implementation, the frequency domain position offset is 0kHz, −7.5 kHz, or 7.5 kHz.

In some embodiments, the frequency domain position offset is −7.5 kHz or7.5 kHz, so that an LTE system can coexist with a future system (forexample, a 5G system).

In a possible implementation, the preset frequency bandwidth of thefrequency resource of a physical resource block meets the followingrelational expression:

F _(RB)=SCS*N _(SC) ^(RB),

where F_(RB) is the predefined frequency bandwidth of the frequencyresource of a physical resource block, SCS is a preset subcarrierspacing of a physical resource block, and N_(SC) ^(RB) is a predefinedsubcarrier quantity of a physical resource block.

In a possible implementation, the predefined subcarrier spacing of aphysical resource block is 15 kHz, and the predefined subcarrierquantity of a physical resource block is 12 or 16.

In a possible implementation, the frequency domain position of thetarget frequency resource includes a frequency domain position of acenter frequency of the frequency resource, a frequency domain positionof a starting frequency of the frequency resource, or a frequency domainposition of an ending frequency of the frequency resource.

According to a second aspect, a synchronization signal receiving methodis provided, including:

obtaining a target frequency resource, where a frequency domain positionof the target frequency resource is determined based on a frequencyinterval of synchronization channels, the frequency interval ofsynchronization channels is 2^(m) times a predefined frequency bandwidthof a frequency resource of a physical resource block, and m is a presetnonnegative integer; and

receiving, based on the target frequency resource, a synchronizationsignal from a base station.

The frequency domain position of the frequency resource occupied by thesynchronization signal is determined based on the frequency interval ofsynchronization channels, and the frequency interval of synchronizationchannels is 2^(m) times the preset frequency bandwidth of the frequencyresource of a physical resource block. This is for the benefit ofincreasing a quantity of candidate frequency resources of thesynchronization signal, thereby increasing available frequency domainmapping positions for the synchronization signal.

In a possible implementation, a starting frequency domain position or anending frequency domain position of the target frequency resource alignswith a boundary of a physical resource block of a data channel.

This can prevent the synchronization signal from occupying an extraphysical resource block, and reduce physical resource block overheads ofthe synchronization signal in a system, thereby improving physicalresource block utilization of the system.

In a possible implementation, the frequency domain position of thetarget frequency resource is determined based on the frequency intervalof synchronization channels and a preset frequency domain positionoffset.

The available frequency domain mapping positions for the synchronizationsignal can be further increased by flexibly defining a value of thefrequency domain position offset.

In a possible implementation, the frequency domain position of thetarget frequency resource is determined according to the followingrelational expression:

p=offset+n*frequency_interval,

where p is the frequency domain position of the target frequencyresource, offset is the frequency domain position offset, n is a presetinteger, and frequency_interval is the frequency interval ofsynchronization channels.

In a possible implementation, n is an integer in an integer set that isdetermined based on a frequency band used by a system.

In this way, candidate frequency resources of the synchronization signalcan be set flexibly based on the frequency band used by the system,thereby further increasing the available frequency domain mappingpositions for the synchronization signal.

In a possible implementation, there is a correspondence between thefrequency band used by the system and the frequency domain positionoffset and/or the frequency interval of synchronization channels, and avalue range of m is determined based on the frequency band used by thesystem.

In this way, candidate frequency resources of the synchronization signalcan be set flexibly based on the frequency band used by the system,thereby further increasing the available frequency domain mappingpositions for the synchronization signal.

In a possible implementation, the frequency domain position offset is 0kHz, −7.5 kHz, or 7.5 kHz.

In some embodiments, the frequency domain position offset is −7.5 kHz or7.5 kHz, so that an LTE system can coexist with a future system (forexample, a 5G system).

In a possible implementation, the predefined frequency bandwidth of thefrequency resource of a physical resource block meets the followingrelational expression:

F _(RB)=SCS*N _(SC) ^(RB),

where F_(RB) is the predefined frequency bandwidth of the frequencyresource of a physical resource block, SCS is a predefined subcarrierspacing of a physical resource block, and N_(SC) ^(RB) is a predefinedsubcarrier quantity of a physical resource block.

In a possible implementation, the predefined subcarrier spacing of aphysical resource block is 15 kHz, and the predefined subcarrierquantity of a predefined physical resource block is 12 or 16.

In a possible implementation, the frequency domain position of thetarget frequency resource includes a frequency domain position of acenter frequency of the frequency resource, a frequency domain positionof a starting frequency of the frequency resource, or a frequency domainposition of an ending frequency of the frequency resource.

According to a third aspect, a base station is provided, where the basestation is configured to implement the method according to any one ofthe first aspect or the foregoing possible implementations of the firstaspect.

Specifically, the base station may include units configured to performthe method according to any one of the first aspect or the possibleimplementations of the first aspect.

According to a fourth aspect, a terminal device is provided, where theterminal device is configured to implement the method according to anyone of the second aspect or the foregoing possible implementations ofthe second aspect.

Specifically, the terminal device may include units configured toperform the method according to any one of the second aspect or thepossible implementations of the second aspect.

According to a fifth aspect, a base station is provided, including aprocessor, a transmitter, a memory, and a bus system, where theprocessor, the transmitter, and the memory are connected by using thebus system, the memory is configured to store instructions or codes, andthe processor is configured to execute the instructions or the codesstored in the memory, so that the base station performs the methodaccording to any one of the first aspect or the possible implementationsof the first aspect.

According to a sixth aspect, a terminal device is provided, including aprocessor, a receiver, a memory, and a bus system, where the processor,the receiver, and the memory are connected by using the bus system, thememory is configured to store instructions or codes, and the processoris configured to execute the instructions or the codes stored in thememory, so that the terminal device performs the method according to anyone of the second aspect or the possible implementations of the secondaspect.

According to a seventh aspect, a computer-readable storage medium isprovided, where the computer readable storage medium stores a program,and the program enables a base station to perform the method accordingto any one of the first aspect or the possible implementations of thefirst aspect.

According to an eighth aspect, a computer-readable storage medium isprovided, where the computer readable storage medium stores a program,and the program enables a terminal device to perform the methodaccording to any one of the second aspect or the possibleimplementations of the second aspect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a frequency domain position of asynchronization channel in a 20 MHz system;

FIG. 2 is a schematic flowchart of a synchronization signal sendingmethod according to an embodiment of this application;

FIG. 3 is a schematic diagram of a frequency domain mapping position ofa synchronization signal;

FIG. 4 is another schematic diagram of a frequency domain mappingposition of a synchronization signal;

FIG. 5 is a schematic flowchart of a synchronization signal receivingmethod according to an embodiment of this application;

FIG. 6 is a schematic structural diagram of a base station according toan embodiment of this application;

FIG. 7 is a schematic structural diagram of a base station according toanother embodiment of this application;

FIG. 8 is a schematic structural diagram of a terminal device accordingto an embodiment of this application; and

FIG. 9 is a schematic structural diagram of a terminal device accordingto another embodiment of this application.

DESCRIPTION OF EMBODIMENTS

The following describes the technical solutions in the embodiments ofthis application with reference to accompanying drawings of theembodiments of this application.

It should be understood that the technical solutions of this applicationmay be applied to various communication systems, for example, WirelessFidelity (WiFi), Worldwide Interoperability for Microwave Access(WiMAX), a Global System for Mobile Communications (GSM), a CodeDivision Multiple Access (CDMA) system, a Wideband Code DivisionMultiple Access (WCDMA) system, a general packet radio service (GPRS), aLong Term Evolution (LTE) system, an Advanced Long Term Evolution(LTE-A) system, a Universal Mobile Telecommunications System (UMTS), andcellular systems related to the 3rd Generation Partnership Project(3GPP). The embodiments of this application set no limitation. However,for ease of description, an LTE network is used as an example fordescription in the embodiments of this application.

The embodiments of this application may be used for wireless networks ofdifferent standards. Radio access networks in different systems mayinclude different network elements. For example, a radio access networkof Long Term Evolution (LTE) and LTE-A includes an evolved NodeB (eNB),and a radio access network of Wideband Code Division Multiple Access(WCDMA) includes a radio network controller (RNC) and a NodeB.Similarly, other wireless networks such as Worldwide Interoperabilityfor Microwave Access (WiMax) may also use a solution similar to theembodiments of this application, except that a related module in a basestation system may vary. The embodiments of this application set nolimitation. However, for ease of description, a base station is used asan example for description in the following embodiments.

It should be further understood that in the embodiments of thisapplication, a terminal device is also referred to as user equipment(UE), a mobile station (MS), a mobile terminal, or the like. Theterminal may communicate with one or more core networks via a radioaccess network (RAN). For example, the terminal may be a mobile phone(or referred to as a “cellular” phone), a computer having acommunication function, or the like. For example, the terminal may alsobe a portable, pocket-sized, handheld, computer built-in, or in-vehiclemobile apparatus.

It should be noted that a frequency interval of synchronization channelsmay be a frequency interval between center frequencies of twosynchronization channels, may be a frequency interval between startingfrequencies of two synchronization channels, or may be a frequencyinterval between ending frequencies of two synchronization channels.

FIG. 2 is a schematic flowchart of a synchronization signal sendingmethod 200 according to an embodiment of this application. It should beunderstood that the method 200 may be performed by a base station. Asshown in FIG. 2 , the method 200 includes the following content.

210. Determine a target frequency resource, where a frequency domainposition of the target frequency resource is determined based on afrequency interval of synchronization channels, the frequency intervalof synchronization channels is 2^(m) times a predefined frequencybandwidth of a frequency resource in a physical resource block, and m isa preset nonnegative integer.

Optionally, the base station may select one or more frequency resourcesfrom a synchronization channel frequency resource set as the targetfrequency resource.

In some embodiments, an interval of at least two frequency resources inthe synchronization channel frequency resource set is an integermultiple of the frequency interval of synchronization channels.

In some embodiments, a synchronization signal frequency resource set mayinclude a plurality of frequency resources. A frequency domain positionof at least one frequency resource in the plurality of frequencyresources is determined based on the frequency interval ofsynchronization channels defined in this embodiment of this application.Alternatively, frequency domain positions of other frequency resourcesin the plurality of frequency resources may be defined according toother preset rules. This embodiment of this application sets nolimitation thereto.

For example, alternatively, frequency domain positions of some frequencyresources in the frequency resource set may be determined based on afrequency interval of synchronization channels in the prior art. Forexample, an LTE protocol defines that a synchronization channel needs tobe located at a frequency that is an integer multiple of 100 kHz infrequency domain, for example, 2 MHz, 2.1 MHz or 2.2 MHz.

In some embodiments, if the target frequency resource includes one ormore frequency resources, the one or more frequency resources may bedetermined based on the frequency interval of synchronization channelsdefined in this embodiment of this application or may be determinedaccording to another preset rule.

220. Send a synchronization signal by using the target frequencyresource.

In this embodiment of this application, the target frequency resource isdetermined based on the frequency interval of synchronization channels,and the frequency interval of synchronization channels is 2^(m) timesthe predefined frequency bandwidth of the frequency resource of aphysical resource block. For example, the predefined frequency bandwidthof the frequency resource of a physical resource block is 180 kHz, andm=0. Then, a value of the frequency interval of synchronization channelsis 180 kHz. Apparently, this embodiment of this application is favorablefor increasing a quantity of candidate frequency resources of thesynchronization signal.

Therefore, in this embodiment of this application, the frequency domainposition of the frequency resource occupied by the synchronizationsignal is determined based on the frequency interval of synchronizationchannels, and the frequency interval of synchronization channels is2^(m) times the predefined frequency bandwidth of the frequency resourceof a physical resource block. This is for the benefit of increasing thequantity of candidate frequency resources of the synchronization signal,thereby increasing available of frequency domain mapping positions forthe synchronization signal.

Optionally, a starting frequency domain position or an ending frequencydomain position of the target frequency resource aligns with a boundaryof a physical resource block of a data channel. This can prevent thesynchronization signal from occupying an extra physical resource block,and reduce physical resource block overheads of the synchronizationsignal in a system, thereby improving physical resource blockutilization of the system.

As shown in FIG. 3 , if the starting frequency domain position of thefrequency resource of the synchronization signal does not align with aboundary of a physical resource block 6 of the data channel, thesynchronization signal occupies physical resource blocks whose indicesare 6 to 12. As shown in FIG. 4 , if the starting frequency domainposition of the frequency resource of the synchronization signal alignswith a boundary of the physical resource block 7 of the data channel,the same synchronization signal occupies physical resource blocks whoseindices are 7 to 12. Apparently, aligning the starting frequency domainposition of the frequency resource with the boundary of the physicalresource block of the data channel can prevent occupation of an extraphysical resource block. Similarly, a same effect can also be achievedby aligning the ending frequency domain position of the frequencyresource with the boundary of the physical resource block of the datachannel. Details are not described herein again.

In some embodiments, the predefined physical resource block may be thesame as the physical resource block of the data channel. In some otherembodiments, alternatively, the predefined physical resource block maybe different from the physical resource block of the data channel. Thisembodiment of this application sets no limitation thereto.

In some embodiments, the frequency interval of synchronization channelsmeets the following relational expression: raster=F_(RB)*2^(m), whereF_(RB) is the predefined frequency bandwidth of the frequency resourceof the physical resource block.

Optionally, there is a correspondence between a value range of m and afrequency band used by a system. For example, a plurality of frequencybands used by the system correspond to a same value range of m, eachfrequency band used by the system corresponds to one value range of m,or each frequency band used by the system corresponds to a plurality ofvalue ranges of m. Before sending the synchronization signal, the basestation may select a determined value from the value range of m, so asto determine the target frequency resource.

The frequency band used by the system may be a 2G frequency band, a 3Gfrequency band, a 4G frequency band, a 5G frequency band, or the like.This embodiment of this application sets no limitation thereto.

In this embodiment of this application, the predefined frequencybandwidth of the frequency resource of the physical resource block isdetermined by a predefined subcarrier spacing and at least onepredefined subcarrier.

For example, the predefined frequency bandwidth of the frequencyresource of the physical resource block meets the following relationalexpression:

F _(RB)=SCS*N _(SC) ^(RB), where

F_(RB) is the predefined frequency bandwidth of the frequency resourceof the physical resource block, SCS is a predefined subcarrier spacingof the physical resource block, and N_(SC) ^(RB) is a predefinedsubcarrier quantity of the physical resource block.

In other words, the predefined physical resource block in thisembodiment of this application consists of N_(SC) ^(RB) subcarriers infrequency domain.

In some embodiments, the predefined subcarrier spacing of the physicalresource block is 15 kHz, and the predefined subcarrier quantity of thephysical resource block is 12 or 16. Correspondingly, the predefinedfrequency bandwidth of the frequency resource of the physical resourceblock is 180 kHz or 240 kHz.

It should be understood that the predefined subcarrier spacing and thepredefined subcarrier quantity of the physical resource block mayalternatively be another value. This embodiment of this application setsno limitation thereto.

For example, the predefined subcarrier spacing of the physical resourceblock may alternatively be 30 kHz, 60 kHz, or the like.

It should be noted that the predefined physical resource block in thisembodiment of this application and a physical resource block in a futuresystem may be the same or may be different.

For example, in the future system (such as a 5G system), a plurality ofsubcarrier spacings may be supported. When the system enables onesubcarrier spacing in a same time resource, the value of the frequencyinterval of synchronization channels may be a frequency bandwidth,determined based on the subcarrier spacing, of a physical resourceblock. In other words, in such a system, m has a unique value. When thesystem enables a plurality of subcarrier spacings in a same timeresource for frequency division multiplexing, a frequency interval ofsynchronization channels mapped to ranges of different subcarrierspacings is a frequency bandwidth of one PRB in a current mapping range.In such a system, a value of m is not unique.

The following uses an example in which one physical resource blockincludes 12 subcarriers for description. For example, the system enablessubcarrier spacings of 15 kHz and 30 kHz in a same time resource. Then,a frequency interval of synchronization channels mapped to a range ofthe 15 kHz subcarrier spacing may be 180 kHz (where a correspondingvalue of m is 0), and a frequency interval of synchronization channelsmapped to a range of the 30 kHz subcarrier spacing may be 360 kHz (wherea corresponding value of m is 1).

Optionally, the frequency domain position of the target frequencyresource is determined based on the frequency interval ofsynchronization channels and a preset frequency domain position offset.

The available frequency domain mapping positions for the synchronizationsignal can be further increased by flexibly defining a value of thefrequency domain position offset.

Optionally, the frequency domain position of the target frequencyresource is determined according to the following relational expression:

p=offset+n*frequency_interval, where

p is the frequency domain position of the target frequency resource,offset is the frequency domain position offset, n is a preset integer,and frequency_interval is the frequency interval of synchronizationchannels.

Optionally, the frequency domain position offset may be 0 kHz, −7.5 kHz,or 7.5 kHz.

For example, when the 5G system is not deployed with an LTE systemcontinuously in a same frequency band, impact of coexistence with LTEmay not be considered for the 5G system, and a value of the frequencydomain position offset may be 0 kHz. Alternatively, the frequency domainposition offset may be other predefined values due to other deploymentflexibility considerations.

When contiguous carrier aggregation is performed between the 5G systemand the LTE system, subcarrier orthogonality with the LTE system needsto be considered in the 5G system. In a design of the LTE system, ablank subcarrier is reserved at a center of a frequency band. A centerof the system frequency band is located at a center of the blanksubcarrier in practice. Therefore, boundaries of all subcarriers of theLTE system is at (n×100 kHz±7.5 kHz). During LTE-to-LTE contiguouscarrier aggregation, both carriers have an offset of 7.5 kHz. Therefore,subcarrier orthogonality can be implemented provided that the frequencyinterval of synchronization channels meets 300 kHz (which is a leastcommon multiple of 100 kHz and the subcarrier spacing of 15 kHz).However, reservation of the blank subcarrier is cancelled in the 5Gsystem. Therefore, during contiguous carrier aggregation between the 5Gsystem and the LTE system, the offset of 7.5 kHz needs to beadditionally compensated for. After the offset of 7.5 kHz is compensatedfor, a frequency interval of synchronization channels of the LTE systemmeets a condition of 300 kHz. In addition, in this embodiment of thisapplication, all frequency intervals of synchronization channels areinteger multiples of 15 kHz. Therefore, this can ensure the subcarrierorthogonality between the 5G system and the LTE system.

Therefore, the frequency domain position offset of −7.5 kHz or 7.5 kHzenables the LTE system to coexist with the future system (for example,the 5G system).

Optionally, there is a correspondence between a value range of n and thefrequency band used by the system. For example, at least one integer setmay be determined based on the frequency band used by the system. Beforesending the synchronization signal, the base station may select, as avalue of n, an integer from an integer set corresponding to a frequencyband currently used by the system. In other words, n is an integer inthe integer set that is determined based on the frequency band used bythe system.

In this way, candidate frequency resources of the synchronization signalcan be set flexibly based on the frequency band used by the system,further increasing the available frequency domain mapping positions forthe synchronization signal.

Optionally, there is a correspondence between the frequency domainposition offset and the frequency band used by the system. For example,a plurality of frequency bands used by the system correspond to a samefrequency domain position offset; each frequency band used by the systemcorresponds to one frequency domain position offset; or each frequencyband used by the system corresponds to a plurality of frequency domainposition offsets, and before sending the synchronization signal, thebase station may select one frequency domain position offset from theplurality of frequency domain position offsets, to determine the targetfrequency resource.

Optionally, there is a correspondence between the frequency interval ofsynchronization channels and the frequency band used by the system. Forexample, a plurality of frequency bands used by the system correspond toa same frequency interval of synchronization channels; each frequencyband used by the system corresponds to one frequency interval ofsynchronization channels; or each frequency band used by the systemcorresponds to a plurality of frequency intervals of synchronizationchannels, and before sending the synchronization signal, the basestation may select one frequency interval of synchronization channelsfrom the plurality of frequency intervals of synchronization channels,to determine the target frequency resource.

In some embodiments, there may be no association relationship betweenthe frequency domain position offset and the frequency interval ofsynchronization channels. For example, the correspondence between thefrequency domain position offset and the frequency band used by thesystem does not affect the correspondence between the frequency intervalof synchronization channels and the frequency band used by the system.For example, a 2G frequency band and a 3G frequency band used by thesystem respectively correspond to different frequency domain positionoffsets but correspond to a same frequency interval of synchronizationchannels.

In some embodiments, there may be a correspondence between the frequencyband used by the system and both the frequency domain position offsetand the frequency interval of synchronization channels. For example, a4G frequency band used by the system corresponds to a first frequencydomain position offset and a first frequency interval of synchronizationchannels, and a 3G frequency band used by the system corresponds to asecond frequency domain position offset and a second frequency intervalof synchronization channels, where the first frequency domain positionoffset is different from the second frequency domain position offset,and the first frequency interval of synchronization channels isdifferent from the second frequency interval of synchronizationchannels.

Optionally, the frequency domain position of the target frequencyresource includes a frequency domain position of a center frequency ofthe target frequency resource.

It should be understood that the frequency domain position of the targetfrequency resource may further include a frequency domain position of astarting frequency of the target frequency resource or a frequencydomain position of an ending frequency of the target frequency resource.This embodiment of this application sets no limitation thereto.

In this embodiment of this application, a frequency domain position of afrequency resource may be indicated by using a frequency correspondingto the frequency resource, or may be indicated by using a number or anindex corresponding to the frequency resource.

FIG. 5 is a schematic flowchart of a synchronization signal detectionmethod 400 according to another embodiment of this application. Itshould be understood that the method 400 may be performed by a terminaldevice. The method 400 corresponds to the method 200, and correspondingcontent is properly omitted herein. As shown in FIG. 5 , the method 400includes the following content.

410. Obtain a target frequency resource, where a frequency domainposition of the target frequency resource is determined based on afrequency interval of synchronization channels, the frequency intervalof synchronization channels is 2^(m) times a predefined frequencybandwidth of a frequency resource of a physical resource block, and m isa preset nonnegative integer.

Optionally, the target frequency resource may be obtained from apreconfigured frequency resource set of a synchronization signal.

It should be understood that the frequency resource set of thesynchronization signal may be preconfigured in the terminal device in apredefined manner or may be preconfigured in the terminal device by abase station.

For example, that the terminal device obtains the frequency resource setof the synchronization signal may include the following: The terminaldevice receives resource configuration information from the basestation, and obtains a resource configuration set of the synchronizationsignal based on the resource configuration information that is of thesynchronization signal and that is sent by the base station.

420. Receive, based on the target frequency resource, a synchronizationsignal from a base station.

For example, before accessing a system, the terminal device firstobtains the frequency resource set of the synchronization signal. Theterminal device cannot have knowledge of specific frequency resources inthe frequency resource set that are used by the base station to send thesynchronization signal. Therefore, the terminal device performs, basedon the frequency resource set of the synchronization signal, blinddetection on the synchronization signal sent by the base station, untilreceiving, by using the target frequency resource, the synchronizationsignal from the base station.

In this embodiment of this application, the frequency domain position ofthe frequency resource occupied by the synchronization signal isdetermined based on the frequency interval of synchronization channels,and the frequency interval of synchronization channels is 2^(m) timesthe predefined frequency bandwidth of the frequency resource of thephysical resource block. This is favorable for increasing a quantity ofcandidate frequency resources of the synchronization signal, therebyincreasing available frequency domain mapping positions for thesynchronization signal.

Optionally, a starting frequency domain position or an ending frequencydomain position of the target frequency resource aligns with a boundaryof the predefined physical resource block.

Optionally, the frequency domain position of the target frequencyresource is determined based on the frequency interval ofsynchronization channels and a preset frequency domain position offset.

Optionally, there is a correspondence between the frequency band used bythe system and the frequency domain position offset and/or the frequencyinterval of synchronization channels, and a value range of m isdetermined based on the frequency band used by the system.

Optionally, the frequency domain position of the target frequencyresource is determined based on the following relationship:

p=offset+n*frequency_interval, where

p is the frequency domain position of the target frequency resource,offset is the frequency domain position offset, n is a preset integer,and frequency interval is the frequency interval of synchronizationchannels.

Optionally, n is an integer in an integer set that is determined basedon the frequency band used by the system.

Optionally, the predefined frequency bandwidth of the frequency resourceof the physical resource block meets the following relationalexpression:

F _(RB)=SCS*N _(SC) ^(RB), where

F_(RB) is the predefined frequency bandwidth of the frequency resourceof the physical resource block, SCS is a predefined subcarrier spacingof the physical resource block, and N_(SC) ^(RB) is a predefinedsubcarrier quantity of the physical resource block.

Optionally, the predefined subcarrier spacing of the physical resourceblock is 15 kHz, and the predefined subcarrier quantity of thepredefined physical resource block is 12 or 16.

Optionally, the frequency domain position offset is 0 kHz, −7.5 kHz, or7.5 kHz.

The frequency domain position offset of −7.5 kHz or 7.5 kHz enables anLTE system to coexist with a future system (for example, the 5G system).

Optionally, the frequency domain position of the target frequencyresource includes a frequency domain position of a center frequency ofthe target frequency resource, a frequency domain position of a startingfrequency of the target frequency resource, or a frequency domainposition of an ending frequency of the target frequency resource.

The foregoing describes the synchronization signal sending method andreceiving method according to the embodiments of this application. Thefollowing describes a base station and a terminal device according tothe embodiments of this application with reference to FIG. 6 to FIG. 9 .

FIG. 6 is a schematic structural diagram of a base station 500 accordingto an embodiment of this application. As shown in FIG. 6 , the basestation 500 includes a processing unit 510 and a sending unit 520.

The processing unit 510 is configured to determine a target frequencyresource, where a frequency domain position of the target frequencyresource is determined based on a frequency interval of synchronizationchannels, the frequency interval of synchronization channels is 2^(m)times a predefined frequency bandwidth of a frequency resource of aphysical resource block, and m is a preset nonnegative integer.

The sending unit 520 is configured to send a synchronization signal byusing the target frequency resource determined by the processing unit510.

In this embodiment of this application, the frequency domain position ofthe frequency resource occupied by the synchronization signal isdetermined based on the frequency interval of synchronization channels,and the frequency interval of synchronization channels is 2^(m) timesthe predefined frequency bandwidth of the frequency resource of thephysical resource block. This is for the benefit of increasing aquantity of candidate frequency resources of the synchronization signal,thereby increasing available frequency domain mapping positions for thesynchronization signal.

It should be understood that the base station 500 according to thisembodiment of this application may correspond to the base station in thesynchronization signal sending method 200 according to the embodiment ofthis application, and the foregoing and other operations and/orfunctions of the units in the base station 500 are respectively intendedto implement corresponding processes in the method 200 shown in FIG. 2 .For brevity, details are not described herein again.

It should be noted that the processing unit 510 may be implemented byusing a processor, and the sending unit 520 may be implemented by usinga transmitter. FIG. 7 is a schematic structural diagram of a basestation 600 according to an embodiment of this application. As shown inFIG. 7 , the base station 600 includes a processor 610, a transmitter620, a memory 630, and a bus system 640. The processor 610, thetransmitter 620, and the memory 630 are connected by using the bussystem 640. The memory 630 may be configured to store code or the likeexecuted by the processor 610. The transmitter 620 is configured to senda signal under control of the processor 610.

It should be understood that the base station 600 according to thisembodiment of this application may correspond to the base station in thesynchronization signal sending method 200 according to the embodiment ofthis application and the base station 500 according to the embodiment ofthis application, and the foregoing and other operations and/orfunctions of the units in the base station 600 are respectively intendedto implement corresponding processes in the method 200 shown in FIG. 2 .For brevity, details are not described herein again.

FIG. 8 is a schematic structural diagram of a terminal device 700according to an embodiment of this application. As shown in FIG. 8 , theterminal device 700 includes a processing unit 710 and a receiving unit720.

The processing unit 710 is configured to obtain a target frequencyresource, where a frequency domain position of the target frequencyresource is determined based on a frequency interval of synchronizationchannels, the frequency interval of synchronization channels is 2^(m)times a frequency bandwidth of a frequency resource in a predefinedphysical resource block, and m is a preset nonnegative integer.

The receiving unit 720 is configured to receive, based on the targetfrequency resource obtained by the processing unit 710, asynchronization signal from a base station.

In this embodiment of this application, the frequency domain position ofthe frequency resource occupied by the synchronization signal isdetermined based on the frequency interval of synchronization channels,and the frequency interval of synchronization channels is 2^(m) timesthe frequency bandwidth of the frequency resource in the predefinedphysical resource block. This is favorable for increasing a quantity ofcandidate frequency resources of the synchronization signal, therebyincreasing available frequency domain mapping positions for thesynchronization signal.

It should be understood that the terminal device 700 according to thisembodiment of this application may correspond to the terminal device inthe synchronization signal receiving method 400 according to theembodiment of this application, and the foregoing and other operationsand/or functions of the units in the terminal device 700 arerespectively intended to implement corresponding processes in the method400 shown in FIG. 5 . For brevity, details are not described hereinagain.

It should be noted that the processing unit 710 may be implemented byusing a processor, and the receiving unit 720 may be implemented byusing a receiver. FIG. 9 is a schematic structural diagram of a terminaldevice 800 according to another embodiment of this application. As shownin FIG. 9 , the terminal device 800 includes a processor 810, a receiver820, a memory 830, and a bus system 840. The processor 810, the receiver820, and the memory 830 are connected by using the bus system 840. Thememory 830 may be configured to store code or the like executed by theprocessor 810. The receiver 820 is configured to receive a signal undercontrol of the processor 810.

It should be understood that the terminal device 800 according to thisembodiment of this application may correspond to the terminal device inthe synchronization signal receiving method 400 according to theembodiment of this application and the terminal device 700 according tothe embodiment of this application, and the foregoing and otheroperations and/or functions of the units in the terminal device 800 arerespectively intended to implement corresponding processes in the method400 shown in FIG. 5 . For brevity, details are not described hereinagain.

It should be noted that in the foregoing embodiments, in addition toincluding a data bus, the bus system may further include a power bus, acontrol bus, and a status signal bus. For ease of representation, thevarious buses are uniformly denoted as the bus system in the figures.

The memory in the foregoing embodiments may include a transitory memory,for example, a random access memory (RAM). The memory may also include anon-transitory memory, for example, a flash memory, a hard disk drive(HDD), or a solid-state drive (SSD). The memory may further include acombination of the foregoing types of memories.

The processor in the foregoing embodiments may be a central processingunit (CPU), a network processor (NP), or a combination of a CPU and anNP. The processor may further include a hardware chip. The foregoinghardware chip may be an application-specific integrated circuit (ASIC),a programmable logic device (PLD), or a combination thereof. Theforegoing PLD may be a complex programmable logic device (CPLD), afield-programmable gate array (FPGA), a generic array logic (GAL), orany combination thereof.

A person of ordinary skill in the art may be aware that the units andalgorithm steps in the examples described with reference to theembodiments disclosed in this specification may be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraint conditions ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of this application.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the system, apparatus, and unit, refer to a correspondingprocess in the method embodiments. Details are not described hereinagain.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electrical, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected based on actualneeds to achieve the objectives of the solutions of the embodiments.

In addition, functional units in the embodiments of this application maybe integrated into one processing unit, or each of the units may existalone physically, or two or more units are integrated into one unit.

When the functions are implemented in a form of a software functionalunit and sold or used as an independent product, the functions may bestored in a computer-readable storage medium. Based on such anunderstanding, the technical solutions of this application essentially,or the part contributing to the prior art, or some of the technicalsolutions may be implemented in a form of a software product. Thecomputer software product is stored in a storage medium, and includesseveral instructions for instructing a computer device (which may be apersonal computer, a server, a network device, or the like) to performall or some of the steps of the methods described in the embodiments ofthis application. The foregoing storage medium includes: any medium thatcan store program code, such as a USB flash drive, a removable harddisk, a read-only memory (ROM), a random access memory (RAM), a magneticdisk, or an optical disc.

The descriptions are only specific implementations of this application,but are not intended to limit the protection scope of this application.Any variation or replacement readily figured out by a person skilled inthe art within the technical scope disclosed in this application shallfall within the protection scope of this application. Therefore, theprotection scope of this application shall be subject to the protectionscope of the claims.

1. A method, comprising: determining, by a terminal device, a targetfrequency resource, wherein a frequency domain position of the targetfrequency resource meets the following relation:p=offset+n*frequency_interval, wherein p is the frequency domainposition of the target frequency resource, offset is a frequency domainposition offset, n is an integer, and frequency_interval is a frequencyinterval of synchronization channels, wherein the frequency interval ofsynchronization channels meets 2^(m) times 180 kHz or 2^(m) times 360kHz, and wherein m is a nonnegative integer; and receiving, by theterminal device using the target frequency resource, a synchronizationsignal.
 2. The method according to claim 1, wherein n is an integer inan integer set that is determined based on a frequency band used by asystem.
 3. The method according to claim 2, wherein a value range of mis determined based on the frequency band used by the system.
 4. Themethod according to claim 1, wherein there is a correspondence between afrequency band used by a system and at least one of the frequency domainposition offset or the frequency interval of synchronization channels.5. The method according to claim 1, wherein the frequency domainposition of the target frequency resource is a frequency domain positionof a center frequency of the target frequency resource, a frequencydomain position of a starting frequency of the target frequencyresource, or a frequency domain position of an ending frequency of thetarget frequency resource.
 6. The method according to claim 1, whereinthe frequency interval of synchronization channels is a frequencyinterval between center frequencies of two synchronization channels, afrequency interval between starting frequencies of two synchronizationchannels, or a frequency interval between ending frequencies of twosynchronization channels.
 7. The method according to claim 1, whereinthe target frequency resource is in a 3 GHz frequency band, a 4 GHzfrequency band, or a 5 GHz frequency band.
 8. An apparatus, comprising:at least one memory including executable instructions; and at least oneprocessor; wherein the executable instructions, when executed by the atleast one processor, cause the apparatus to: determine a targetfrequency resource, wherein a frequency domain position of the targetfrequency resource meets the following relation:p=offset+n*frequency_interval, wherein p is the frequency domainposition of the target frequency resource, offset is a frequency domainposition offset, n is an integer, and frequency_interval is a frequencyinterval of synchronization channels, wherein the frequency interval ofsynchronization channels meets 2^(m) times 180 kHz or 2^(m) times 360kHz, and wherein m is a nonnegative integer; and receive asynchronization signal by using the target frequency resource.
 9. Theapparatus according to claim 8, wherein n is an integer in an integerset that is determined based on a frequency band used by a system. 10.The apparatus according to claim 9, wherein a value range of m isdetermined based on the frequency band used by the system.
 11. Theapparatus according to claim 8, wherein there is a correspondencebetween a frequency band used by a system and at least one of thefrequency domain position offset or the frequency interval ofsynchronization channels.
 12. The apparatus according to claim 8,wherein the frequency domain position of the target frequency resourceis a frequency domain position of a center frequency of the targetfrequency resource, a frequency domain position of a starting frequencyof the target frequency resource, or a frequency domain position of anending frequency of the target frequency resource.
 13. The apparatusaccording to claim 8, wherein the frequency interval of synchronizationchannels is a frequency interval between center frequencies of twosynchronization channels, a frequency interval between startingfrequencies of two synchronization channels, or a frequency intervalbetween ending frequencies of two synchronization channels.
 14. Theapparatus according to claim 8, wherein the target frequency resource ison a 3 GHz frequency band, a 4 GHz frequency band, or a 5 GHz frequencyband.
 15. A non-transitory computer-readable storage medium storinginstructions that, when executed by at least one processor, cause anetwork device to carry out the following: determining a targetfrequency resource, wherein a frequency domain position of the targetfrequency resource meets the following relation:p=offset+n*frequency_interval, wherein p is the frequency domainposition of the target frequency resource, offset is a frequency domainposition offset, n is an integer, and frequency_interval is a frequencyinterval of synchronization channels, wherein the frequency interval ofsynchronization channels meets 2^(m) times 180 kHz or 2^(m) times 360kHz, and wherein m is a nonnegative integer; and receiving asynchronization signal by using the target frequency resource.
 16. Thenon-transitory computer-readable storage medium according to claim 15,wherein n is an integer in an integer set that is determined based on afrequency band used by a system.
 17. The non-transitorycomputer-readable storage medium according to claim 16, wherein a valuerange of m is determined based on the frequency band used by the system.18. The non-transitory computer-readable storage medium according toclaim 15, wherein there is a correspondence between a frequency bandused by a system and at least one of the frequency domain positionoffset or the frequency interval of synchronization channels.
 19. Thenon-transitory computer-readable storage medium according to claim 15,wherein the frequency domain position of the target frequency resourceis a frequency domain position of a center frequency of the targetfrequency resource, a frequency domain position of a starting frequencyof the target frequency resource, or a frequency domain position of anending frequency of the target frequency resource.
 20. Thenon-transitory computer-readable storage medium according to claim 15,wherein the target frequency resource is on a 3 GHz frequency band, a 4GHz frequency band, or a 5 GHz frequency band.